Astrophysics > Instrumentation and Methods for Astrophysics

Abstract: We study the image formation process with the solar gravitational lens (SGL)
in the case of an extended, resolved source. An imaging telescope, modeled as a
convex lens, is positioned within the image cylinder formed by the light
received from the source. In the strong interference region of the SGL, this
light is greatly amplified, forming the Einstein ring around the Sun,
representing a distorted image of the extended source. We study the intensity
distribution within the Einstein ring observed in the focal plane of the convex
lens. For any particular telescope position in the image plane, we model light
received from the resolved source as a combination of two signals: light
received from the directly imaged region of the source and light from the rest
of the source. We also consider the case when the telescope points away from
the extended source or, equivalently, it observes light from sources in sky
positions that are some distance away from the extended source, but still in
its proximity. At even larger distances from the optical axis, in the weak
interference or geometric optics regions, our approach recovers known models
related to microlensing, but now obtained via the wave-optical treatment. We
then derive the power of the signal and related photon fluxes within the
annulus that contains the Einstein ring of the extended source, as seen by the
imaging telescope. We discuss the properties of the deconvolution process,
especially its effects on noise in the recovered image. We compare anticipated
signals from realistic exoplanetary targets against estimates of noise from the
solar corona and estimate integration times needed for the recovery of
high-quality images of faint sources. The results demonstrate that the SGL
offers a unique, realistic capability to obtain resolved images of exoplanets
in our galactic neighborhood.